Method for electrical induction, heat treatment for railroad switches (rail tongues, crossings, wing rails)

ABSTRACT

A railroad-switch component of irregular cross section is moved through an induction-heating station along with a nonmagnetic conductive body. This body fits the nonuniform switch component complementarily to give the two an overall uniform cross section at least over the significant portion of the rail or tongue, so that they can be moved at a uniform speed and heated with a uniform flux to surface harden the top of the switch component for example. Subsequently the two are quenched and the bottom of the rail component is heated.

United States Patent [72] Inventors Grigore Niculescu Bucharest; Tralan Ghlmbasean, Bucharest; Eugen Dumitrescu, Bucharest; Nicolae Ionescu,

Buzau, all of Romania [21] Appl. No. 741,166

[ 22] Filed June 28, I968 [45] Patented Nov. 23, 1971 73] Assignee Instltutul de Cercetari Tehnologice Pentru Constructii dc Masini Bucharest, Romania [32] Priority June 29, 1967 3 3] Romania [54] METHOD FOR ELECTRICAL INDUCTION, HEAT TREATMENT FOR RAILROAD SWITCHES (RAIL TONGUES, CROSSINGS, WING RAILS) 6 Claims, 2 Drawing Figs.

[52] U.S.Cl 148/146, 148/149, 148/150, 148/152, 148/154 [51] Int. Cl C21d 1/00 [50] Field of Search 148/145, 146,149, 150,152,154

[56] References Cited UNITED STATES PATENTS 882,162 3/1908 Painter 148/145 2,572,201 10/1951 Rooke 148/146 Primary Examiner-Richard 0. Dean Attorney-Karl F. Ross ABSTRACT: A railroad-switch component of irregular cross section is moved through an induction-heating station along with a nonmagnetic conductive body. This body fits the nonuniform switch component complementarily to give the two an overall uniform cross section at least over the significant portion of the rail or tongue, so that they can be moved at a uniform speed and heated with a uniform flux to surface harden the top of the switch component for example. Subsequently the two are quenched and the bottom of the rail component is heated.

PAIENTEnunv 23I97| 3,622.40?

Grigore Niculescu Traiun Ghimbosean Eugen Dumitrescu Nicolae -lonescu /n venfom METHOD FOR ELECTRICAL INDUCTION, HEAT TREATMENT FOR RAILROAD SWITCHES (RAIL TONGUES, CROSSINGS, WING RAILS) Our invention relates to a method of heat treating the stressed parts of rail tongues, crossings, and wing rails to surface harden them.

Often the wear-prone components of railroad switches are made of high alloy steel. Such compositions necessitate the laborious and very expensive production of the alloy with use of extremely expensive metals such as vanadium, chromium, manganese and molybdenum. Otherwise the railroad-switch components are simply made from surface-hardened steel. This surface hardening has generally been carried out heretofore with the use of a system of burners through which the rail components are moved.

When these flame heat treatments are employed, a constant regulation of the heating energy and of the cooling or quenching medium must be carried out to compensate for the continuously varying cross section of the rail tongue, crossing, or of the wing rail. Furthermore this treated zone has a strict horizontal structure lacking any adaptation to the particular contours of the component involved.

The amount of heat to which the component is subjected in the above-mentioned method is controlled either by varying the fuel fiow according to the cross section, or by varying the speed of the component as it passes through the system. Obviously, such a method is cumbersome and lacks efficiency.

It is an object of our invention to heat treat such irregularly shaped steel bodies as railroad switch components by an improved, simple and inexpensive method requiring less regulation than earlier systems.

This object is attained according to the main feature of our invention by heating the components through thermoelectric induction and rendered easy by fitting a nonmagnetic metal body (i.e.) relatively low magnetic permeability) to the body to be treated. In this way a constant magnetic flux or applied induction-heating current can be used to treat a nonuniform steel body moving at a constant speed. The nonmagnetic body is preferably made of copper and serves to distribute the eddy currents between itself and the steel body, thereby preventing overheating even if the steel body has relatively thin portions; however due to its nonmagnetic properties, the copper body does not uselessly absorb electrical energy. It is of course reusable.

After heat treating the iron or steel body for surface hardening, it is moved with the copper body under a nozzle emitting a fine spray of water and then under a device which sprays more water over it to quench it. Subsequent or simultaneous heating of the bottom of the component tends to prevent bowing for the same thereby eliminating the need of any mechanical straightening equipment.

This method makes for easy surface hardening of irregularly shaped pieces of steel with a minimum of equipment, the method being easily incorporated into the production line of a rolling mill. In addition the finished product has a service life some 3 to times greater than the conventional components, and offers extremely strong bow-shaped hardened layers on all upper surfaces, unfissured and undamaged by flame.

The above and other objects, features and advantages will be more readily apparent from the following description, reference being made to the accompanying drawing, in which:

FIG. I shows a plant, in diagrammatic perspective view, for carrying out the method of my invention; and

FIG. 2 is a cross section through a portion of the plant of FIG. 1.

As seen in FIG. 1, an AC generator I producing a constant energy of 250 kw. at 2,500 Hz. is connected to a transformer 3. A capacitor 2 or bank of capacitors connected across the input winding of this transformer 3 compensates for the wattless component of the generator 1. The output winding of this transformer 3 is connected to an inductor loop 4 or one of a plurality of loop stages located above a surface-hardening ath. p A rail 5 having a rail tongue 5a is moved along this path at a constant speed in the direction of an arrow A along with a copper compensating body 6 complementarily fitting the tongue 5a and lying thereagainst although illustrated with a slight spacing therefrom.

Downstream of the inductor 4 is a nozzle 7 for the airatomized spraying of water on the rail 5. Yet further downstream is a sprayer 8 which can prevent or interrupt the tempering process as desired through controlled quenching of the rail 5. At the further downstream end is a second inductor 9 connected to a transformer 10 for heating the bottom of the rail 5 to prevent the same from bowing.

The surface hardening is carried out as follows:

As the rail 5 moves in the direction A its upper surface is heated by internal eddy currents generated in it by the inductor 4. However, as seen in FIG. 2, in places where the rail 5 has a thin section which could lead to overheating, it is protected by the copper body 6.

The flux in the direction I, in the inductor 4 (FIG. 2) flows in directions I and L, in the tongue 5a and the body 6 respectively. Thus, as the rail 5 and the body 6 move through, they always present a uniform cross section to the inductor so that hardening and heating of the body 5 is carried out to the same extent over its entire length in spite of its irregularities.

After heating, the two are cooled by the nozzle 7 and the sprayer 8 and the bottom of the rail 5 is heated by the second inductor 9 to finish the process. The finished product here has a surface hardness of up to 45-50 on the Rockwell scale, and is found to have bow-shaped heat-treated zones of a thickness of 9-11 mm. The ultimate tensile strength of the heat-treated layer is more than kp/mmF.

The improvement described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the invention except as limited by the appended claims.

We claim:

1. A method of heat treating an elongated iron body of nonuniform cross section to surface harden it comprising the steps of:

longitudinally displacing said iron body together with at least one elongated nonmagnetic metal body at a substantially constant rate, said nonmagnetic body being disposed laterally adjacent said iron body and being generally complementary to said iron body over at least part of its length whereby said bodies jointly have a substantially uniform cross section over at least partof the thickness of said iron body;

induction heating said bodies with a substantially constant flux level as they are longitudinally displaced; and thereafter quenching said iron body.

2. The method defined in claim 1 wherein said elongated iron body is a steel railroad-switch component and the heat treating is carried out to harden upper stressable portions of said component, said method further comprising the step of heating a lower portion of said component to prevent bowing of same.

3. The method defined in claim 2 wherein said steel component body is quenched with water.

4. The method defined in claim 3 wherein at least a portion of said water is atomized with air and sprayed onto said steel component.

5. The method defined in claim 2 wherein said lower portion is heated by induction heating.

6. The method defined in claim 5 wherein said lower portion is heated by induction heating subsequent to the quenching. 

2. The method defined in claim 1 wherein said elongated iron body is a steel railroad-switch component and the heat treating is carried out to harden upper stressable portions of said component, said method further comprising the step of heating a lower portion of said component to prevent bowing of same.
 3. The method defined in claim 2 wherein said steel component body is quenched with water.
 4. The method defined in claim 3 wherein at least a portion of said water is atomized with air and sprayed onto said steel component.
 5. The method defined in claim 2 wherein said lower portion is heated by induction heating.
 6. The method defined in claim 5 wherein said lower portion is heated by induction heating subsequent to the quenching. 